Dust-free bench



y 9, 7 A. K. BAKER 3,318,076

DUST-FREE BENCH Filed Aug. 14, 1964 3 Sheets-Sheet 1 H66 z L \U f 34 a?39'" a 35 39- j: a? 37 40 T 15 40 R: 7 )NVEFJOR. V ARTHUR K. BAKER BY fSM ATTORNEY 1967 A. K. BAKER 3,318,076

DUST-FREE BENCH Filed Aug. 14, 1964 3 Sheets-$fieet 2 F 35 l 3 24 I I4II II II' II TITI II II II II II II II II Ir" INVENTOR. ARTHUR K. BAKERf? /wfi ATTORNEY United States Patent 3,318,076 DUST-FREE BENCH ArthurK. Baker, Chandler, Ariz., assignor, by mesne assignments, to Arthur K.Baker and Esther M. Baker, Chandler, Ariz.

Filed Aug. 14, 1964, Ser. No. 389,581 4 Claims. (Cl. 55-350) Thisinvention relates generally to dust-free benches and has reference moreparticularly to a bench of this character having novel means formaintaining a dust-free upper working surface and a dust-free workingspace thereabove.

Duse-free benches as heretofore constructed generally provide for themovement of air substantially over the upper surface of the benchflowing as from the back thereof or from above, but such prior typebenches do not prevent the lodging of dust on the bench surface, nor dothey prevent dust from entering the open front of the bench, due to backflow of air currents produced by various causes such as eddy currentsand backwash produced as by work lying upon the bench obstructing thenormal flow of air, or by the worker, himself.

The principal object of the present invention is to provide a noveldust-free bench that is so constructed and arranged as to direct highlyfiltered air over the bench surface in smooth laminar or uniform flow,thereby maintaining a zone of dust-free air over the surface of thebench and throughout the working space above the same, the free edge oredges of the bench and the edges of the hood or dividing partitionsadjacent to the bench working area having apertures, means beingprovided for drawing air inwardly through said apertures, wherebyturbulent air due, for example to irregular flow over objects on thebench or the workers movements and the eddy currents or backwashcurrents produced thereby are sucked in through the openings at thefront of the bench and along the side edges of the hood or dividingpartitions, thereby preventing external dust-laden air from entering thebench working area and depositing dirt thereon.

A feature of the present invention is to provide a novel, dust-freebench of the above character wherein an exceptionally clean environmentover the bench and within the working space results in the recirculationof some of the same air over and over through the system, i.e., most ofthe air flowing only over the bench instead of flowing on into the roomand becoming contaminated, being drawn back into the filter system ofthe bench through the openings in the hood or dividing partitions and inthe bench top.

Another feature of the present invention is to provide a dust-free benchof the above character that eliminates operator discomfort, since mostof the air flowing over the bench is sucked back into the bench interiorand is not felt by the operator, the novel circulating method of thepresent invention enabling the use of a fully open front hood, forexample, and hence easy access to the interior thereof without anydanger of contamination, the hood top when used preferably overlying theforward edge of the bench to prevent dust or other particles fromfalling on the bench from above.

Still another feature of the present invention is to provide a novelbench of the above character wherein the velocity of the air passingoutwardly of the hood toward the operator can be kept relatively low soas to eliminate operator discomfort while higher velocities exist overthe bench working surface and still higher velocities are present in theair being drawn into the hood or dividing partition side edges and orinto the bench free edge.

These and other features and advantages of the present invention will bemore apparent after a perusal of the 3,318,076 Patented May 9, 1967 "icefollowing specification taken in connection with the accompanyingdrawings, wherein:

FIG. 1 is a perspective view of one form of the novel dust-free bench ofthe present invention with arrows indrcating the flow of the air overthe bench within the hood and into the openings at the bench front andhood side edges;

FIG. 2 is a side View with parts broken away of the bench of FIG. 1 andalso shows circulation of air throughout the bench and hood structure inuse;

FIG. 3 is a front view taken of the bench of FIG. 2 with parts brokenaway;

FIG. 4A is a fragmentary schematic view illustrating the formation ofeddy currents and the drawing of dust onto the bench top where thesuction slots are not provided in the bench top and in the hood sides;

FIG. 4B is a view similar to FIG. 4A illustrating the air circulationwhen using the slots of this invention;

FIG. 5 shows a plurality of benches arranged in tandem for a pluralityof workers; and

FIG. 6 is a plan view of the structures of FIG. 5.

Similar characters of reference are used in the above figures todesignate corresponding parts.

Referring now to the drawings, the reference numeral 1 designates abench housing or casing providing an interior lower chamber 2 having amotor 3 therewithin positioned for driving a blower 4 that sucks acontrollable amount of external air in through an adjustable area gridor grille 5, as of the type used in wood-burning or coalburning stovesor in forced-air heating systems and well known to those skilled in theart, said grid being located at the front of the housing and also sucksair from a bench plenum chamber or duct 6 within a hollow horizontalbench 12 through openings 7 in the bench bottom wall communicating withthe interior of housing lower chamber 2. The bench is shown as having ahood 14 provided with side partitions or walls 11 and 11 that are alsohollow providing therewithin side wall plenum chambers or ducts 8 and 8provided with lower apertures 9 provided in inverted channel stiffeningmembers 10 provided at the interior lower edges of the hollow hood sidewalls 11 and 11'. The hollow bench 12 has spaced top and bottom wallsproviding the plenum chamber or duct 6 therebetween and is shown havingits upper working surface 12 interiorly reinforced by reinforcingmembers 13.

The forward edge portion 42 of the hollow bench 12 and the forward edgeportions 43, 43' of the hollow side Walls 11 and 11 are ventedcontiguous to the interior working area of the bench by being providedwith a series of mutually spaced slots arranged in rows and designated15 in the bench forward free edge and 16 in the partitions or hood sides11 and 11 so that air drawn in by the blower 4 not only passes inthrough grid 5 in controlled amounts depending upon the adjustment ofthis grid, but also flows in through the slots 16 at the inner sides ofthe partitions 11 and 11' and through the hood plenum chambers 8 and 8',through apertures 9 and corresponding aperture 9' in the upper surface12' of the bench, and into the bench plenum chamber or duct 6 and fromthence to openings 7 into the lower chamber 2. Likewise, air will flowin through slots 15 of the bench top through the plenum chamber 6,through apertures 7, and to the blower 4. This air is then driven by theblower 4 through the bench circulatory system as will further appear.

The adjustable area grid 5 is shown provided with a primary or coarsefilter 17, and a similar filter is shown provided at 18 at the intake ofthe blower 4. Actually, the coarse filter 17 may be eliminated, ifdesired. The blower 4 forces the air upward into the rear hood plenumchamber or duct 19 provided within casing 1, whence this air flowsthrough a fine or positive filter 20 that may be a mechanical filterhaving a fine screen composed of cellulose glass material, for example.This filter is of rectangular shape and is made somewhat larger than thehood interior 21 so that there will be a uniform flow of air from thefine filter 20 and through a grille 22 into the interior of the hoodchamber 21, whereby there is no opportunity for eddy currents to beformed around the edges of the filter within the hood which wouldotherwise take place should the filter have a solid frame portionprojecting into the confines of the hood interior 21.

The multi-apertured grille 22. directs the air from the filter forwardand parallel to the side and top interior walls of the hood 14 and alsoprotects the filter 21) against physical damage, the air passing overthe surface of the bench 12, providing a uniform laminar flow of airforwardly through the hood in use.

The filter is removably retained within its position in the plenumchamber 19 by means of wedge members 23 or screws or other means andangle type guides 24 attached to the side interior walls of thecasing 1. When the filter is used up, it can be removed by opening thetop hinged section 25, whereupon the wedges 23 can be removed, allowingthe filter to be replaced, the replacement of the wedges serving to holdthe new filter in place so as to completely cover the grille 22. Theupper part of the hood 14 over the bench 12 is provided with a lightingchamber 26 containing fluorescent lights 27 which shine through atranslucent plate 23 provided at the top of the hood chamber 21.

All surfaces in the hood chamber are smooth and are arranged for smoothflow of air throughout the interior 21. As the air moves forward withinthe chamber 21 it reaches the forward edges of the hood wall partitionsides of the bench and a certain amount of this air is sucked into theslots 15 and 16 due to the suction of fan 4, so that only a portion ofthe air leaving filter 20 moves forward :and out of the hood 14. Theslots 15 and 16, being subject to interior negative pressure, preventthe formation of any eddy currents at the front of the bench which mighttend to draw dirt back onto the bench. For example, the work piece 29,resting on top of the bench 12, would ordinarily set up eddy currentsdue to the flow of air thereover, as illustrated in FIG. 4A, the eddycurrents being in front of the work piece, and these currents whirlingaround would suck in contaminated air from the room surrounding thebench and from the operators clothing and hands so that dust would bedeposited upon the bench and upon the work, which is highlyobjectionable.

On the other hand, by using the slots 15 and 16, the eddy currents areeliminated as shown by the circulation of air as indicated in FIG. 4B,for example. Actual tests have shown that where the slots 15 and 16 arenot present, definite quantities of dirt will move onto the bench topand onto the work on the bench, but where these slots are used, no suchdust can enter, because it will be sucked into the slots 15 and 16, andthence through the blower to be eliminated from the circulating system.

FIG. 4A shows in detail the formation of eddy currents by a piece ofwork on the bench where the slots 15 and 16 are not employed, these eddycurrents serving to draw in dust and deposit it upon the bench and uponthe work. Since a lot of the air blown through the hood is sucked backinto the circulating system, a much cleaner environment is providedwithin the work space than would otherwise be the case, and as aconsequence of such recirculation, the life of the filter is greatlyprolonged, since dust from the surrounding room is not drawn into thesystem 7 except that passing through the adjustable grid 5, the

load on both coarse and fine filters is reduced greatly. The apertures 9are so proportioned that ordinarily air is sucked into apertures 16 atthe sides of the hood at a much higher velocity than the air movingforward from filler 20 through the work space. Also, the air movingbackwardly through slots 15 at the front of the bench top flows at ahigher velocity than the air moving from the filter 20 forwardly overthe work space. In a typical instance, air may flow through filter 20and through work space at a velocity of feet a minute, whereas thevelocity intake at the slots 16 at the sides of the hood may be as highas 2000 feet a minute. Since a large portion of the air moving forwardlythrough the work space is drawn back into the circulating system, theoperator feels no uncomfortable draft from the operation of the bench.

Through the use of the vented slots 16 and 15 in the side partitionwalls 11 and 11 of the hood and in the front of the bench, it ispossible to have a fully open hood, or the hood may be eliminatedentirely if desired, enabling easy access to the work on the bench top12 without interference from any windows or panels. Also, highervelocities of air can be passed through the work space since much of itis withdrawn at the forward edges of the same.

In FIGS. 5 and 6 there is illustrated a continuous bench 40 adapted toprovide a number of working spaces for a plurality of workers. In thesefigures filtered air from fine filter 20 passes through ducts 30, 31,32, 33, etc., to hollow side partition walls 34, 35, 36, etc., andthrough grilles 37 transversely across the work spaces 38, 38, 38", etc.and into plenum chambers 39, 39', etc., from whence the air fiows backto blower 4 through coarse filter 18. A grid 5 can be set to allow adesired amount of exterior air to enter the circulating system. In thesefigures the slots 15 are provided in the front edges of the hollow benchand if it is desired to have two workers in each working space slots 15are provided in the rear edge of the bench where the second row ofworkers sit, in which case the bench is made wider to accommodate theextra row of workers. Where only one row of workers is used the backwall of the bench can be closed, if desired, in which case the slots 15would not be essential. Slots 15 and 15 are connected through the hollowbench plenum and apertures 7 to the interior of casing 1' leading toblower 4, whereby suction applied to slots 15 and 15' prevents dust anddirt from moving onto the bench working spaces between the sidepartition walls 34, 35, 36, etc.

Since many changes could be made in the above construction of the noveldust-free bench of this invention and many apparently widely differentembodiments of this invention could be made without departing from thescope thereof, it is intended that all matter contained in the abovedescripion or shown in the accompanying drawings shall be interpreted asillustrative and not in a limiting sense.

What is claimed is: V

1. A dust-free bench structure comprising a bench housing, a hollowbench having a substantially impervious and horizontal upper workingsurface and a spaced lower surface, said surfaces terminating at thefront of said bench in a forward edge portion, said bench beingsupported upon said housing and projecting forwardly thereof to provideknee-space therebelow, said hollow bench defining a duct therewithin andbeing provided with a series of mutually spaced apertures arranged in atranverse row along the forward edge portion thereof communicating withsaid duct, the upper working surface of said bench being substantiallyhorizontal for supporting work thereon and extending to said aperturesat the forward edge portion thereof, said bench duct communicating withthe interior of said bench housing, a blower within said housing havingits input communicating through said housing and said bench duct withsaid apertures, a coarse filter at the intake of said blower forfiltering air sucked in use through said bench forward apertures andthrough said duct and entering a d housing, a fine filter positionedadjacent said hollow bench, a mulit-apertured grille adjoining saidbench working surface and extending substantially perpendicularly to andsubstantially vertically above the same, and an output duct connectingthe output of said blower to said multi-aperturcd grille and includingsaid fine filter for driving air through the latter and through saidgrille, said grille serving to direct the air over said bench workingsurface in substantially laminar flow, a portion of this air beingsucked back in through said bench forward apertures and returned to saidblower in use, thereby effecting recirculation of such air, thusly notonly providing a cleaner environment above the work bench but alsopreventing the ingress of outside contaminated air resulting, in the theabsence of said apertures, from the production of eddy currents over theforward upper surface of the bench due to the presence of work thereonor of the operators hands, as Well as reducing the velocity of air flowpast the bench operator and improving his comfort.

2. A dust-free bench structure as defined in claim 1 wherein saidhousing has a front wall provided with an opening, a grid mounted in theopening of said housing front wall, said grid communicating through theinterior of said housing with the intake of said blower and coarsefilter, for permitting a controlled volume of outside air to enter saidhousing and mix with the returning air from said bench duct beforeentering said coarse filter at the intake of said blower, thuscontrolling the speed and volume of the air entering said bench forwardapertures, to suit a desired environment, said bench forward row ofapertures extending substantially completely across the front edge ofsaid bench.

3. A dust-free bench structure as defined in claim 2 comprising a hoodhaving a hollow top and side walls and open at its front overlying saidbench and supported by said housing, said hood hollow side walls havingducts thereWithin and being provided with a series of mutually spacedapertures along the forward edges only thereof communicating with saidside wall ducts, said side wall ducts communicating at the lower edgesof said side walls with the interior of said bench housing and throughsaid housing interior to the input of said blower, said fine filterbeing positioned at the rear of said hood for directing filtered airtherethrough and over said bench, said blower in use serving to suck airin through said hood side wall forward apertures, through said side wallducts, into the interior of said bench housing, wherein the same mixeswith air entering said housing from said bench duct and from said grid,such mixed air then passing through said coarse filter, said blower andconnected output duct to and through said fine filter.

4. A dust-free bench structure as defined in claim 3 wherein the forwardmutually spaced apertures in each hood side Wall extend in a row forsubstantially the full height of the interior of said hood, stiffeningmembers within the hollow interior of said hood side walls and fixedthereto adjacent said bench upper working surface, and stiffeningmembers within said hollow bench and fixed therewithin, said hoodstiffening members and said bench upper working surface being aperturedto enable air from said side wall ducts to enter said housing, saidstiffening member and bench apertures being of sufi'icient size as tocause return air to enter said hood side apertures at a higher speedthan that of the air flowing forwardly over said bench working surface.

References Cited by the Examiner UNITED STATES PATENTS 1,194,527 8/ 1916McNamara.

2,150,252 3/1939 Shure 98-36 X 2,172,944 9/ 1939 Norris 98-40 2,291,2207/ 1942 Germonprez.

2,332,174 10/1943 Shreve 98-36 X 2,341,628 2/ 1944 Koweindl.

2,999,448 9/ 1961 Abler et al.

3,021,776 2/ 1962 Kennedy.

3,123,988 3/1964 Richman 98-36 X 3,158,457 11/ 1964 Whitfield -473 X3,229,611 1/1966 Berger.

OTHER REFERENCES Crane, V. 6.: Design Techniques for Industrial CleanRooms in Air Conditioning, Heating and Ventilating, pp. 58 to 63.December 1963.

HARRY B. THORNTON, Primary Examiner.

FRANK W. LUTTER, B. NOZICK,

Assistant Examiners.

1. A DUST-FREE BENCH STRUCTURE COMPRISING A BENCH HOUSING, A HOLLOWBENCH HAVING A SUBSTANTIALLY IMPERVIOUS AND HORIZONTAL UPPER WORKINGSURFACE AND A SPACED LOWER SURFACE, SAID SURFACES TERMINATING AT THEFRONT OF SAID BENCH IN A FORWARD EDGE PORTION, SAID BENCH BEINGSUPPORTED UPON SAID HOUSING AND PROJECTING FORWARDLY THEREOF TO PROVIDEKNEE-SPACE THEREBELOW, SAID HOLLOW BENCH DEFINING A DUCT THERWITHIN ANDBEING PROVIDED WITH A SERIES OF MUTUALLY SPACED APERTURES ARRANGED IN ATRANSVERSE ROW ALONG THE FORWARD EDGE PORTION THEREOF COMMUNICATING WITHSAID DUCT, THE UPPER WORKING SURFACE OF SAID BENCH BEING SUBSTANTIALLYHORIZONTAL FOR SUPPORTING WORK THEREON AND EXTENDING TO SAID APERTURESAT THE FORWARD EDGE PORTION THEREOF, SAID BENCH DUCT COMMUNICATING WITHTHE INTERIOR OF SAID BENCH HOUSING, A BLOWER WITHIN SAID HOUSING HAVINGITS INPUT COMMUNICATING THROUGH SAID HOUSING AND SAID BENCH DUCT WITHSAID APERTURES, A COARSE FILTER AT THE INTAKE OF SAID BLOWER FORFILTERING AIR SUCKED IN USE THROUGH SAID BENCH FORWARD APERTURES ANDTHROUGH SAID DUCT AND ENTERING SAID HOUSING, A FINE FILTER POSITIONEDADJACENT SAID HOLLOW BENCH, A MULIT-APERTURED GRILLE ADJOINING SAIDBENCH WORKING SURFACE AND EXTENDING SUBSTANTIALLY PERPENDICULARLY TO ANDSUBSTANTIALLY VERTICALLY ABOVE THE SAME, AND AN OUTPUT DUCT CONNECTINGTHE OUTPUT OF SAID BLOWER TO SAID MULTI-APERTURED GRILLE AND INCLUDINGSAID FINE FILTER FOR DRIVING AIR THROUGH THE LATTER AND THROUGH SAIDGRILLE, SAID GRILLE SERVING TO DIRECT THE AIR OVER SAID BENCH WORKINGSURFACE IN SUBSTANTIALLY LAMINAR FLOW, A PORTION OF THIS AIR BEINGSUCKED BACK IN THROUGH SAID BENCH FORWARD APERTURES AND RETURNED TO SAIDBLOWER IN USE, THEREBY EFFECTING RECIRCULATION OF SUCH AIR, THUSLY NOTONLY PROVIDING A CLEANER ENVIRONMENT ABOVE THE WORK BENCH BUT ALSOPREVENTING THE INGRESS OF OUTSIDE CONTAMINATED AIR RESULTING, IN THEABSENCE OF SAID APERTURES, FROM THE PRODUCTION OF EDDY CURRENTS OVER THEFORWARD UPPER SURFACE OF THE BENCH DUE TO THE PRESENCE OF WORK THEREONOR OF THE OPERATOR''S HANDS, AS WELL AS REDUCING THE VELOCITY OF AIRFLOW PAST THE BENCH OPERATOR AND IMPROVING HIS COMFORT.